1. Field of the Invention
This invention relates to a process and a device for controlling at least one twine guide arm in a pickup baler for wrapping cylindrical bales.
Such a baler, as described in publication FR-A-2 541 560 provides for picking up of windrows and rolling them into a spiral within an expandable baling chamber until the bale completely fills the same.
The bale is then surrounded by a twine helically wound around the bale and then ejected from the baler.
The wrapping or tying of the bale requires sustained attention on the part of the baler driver. On the one hand, the twine guide arm must be correctly placed at the beginning of the tying process and, on the other hand, the movement of the arm must be slow enough for winding the twine around the bale a number of times sufficient to render the bale compact.
2. Description of Related Art
French publication FR-A-2 442 577 describes a baler in which the guide arm is pivoted by means of a traction cable operated by the driver.
Tying devices are also known in which the guide arm is moved in a back and forth movement by a motorized control device, manual intervention possibly being necessary to adjust the speed of the motor or to stop it.
To overcome this drawback, French publication FR-A-2 414 295 provides means for controlling the movement of the guide arm by the bale itself when the latter has reached a predetermined size. For this purpose, the bale actuates a device for actuating a gear motor provided for controlling the tying device.
U.S. patent specification No. 4 649 812 discloses a hay baler of the kind considered herein, which is provided with a twine guide control mechanism having a control cam. Said cam by the action of which the wrapping or tying process is controlled is rotated stepwise by a motor-driven crank that permanently cooperates with a gear integral with said cam.
The present invention is aimed, i.a., at providing a structure wherein the cam can be conveniently engaged or disengaged kinetically with respect to the remainder of the tying control mechanism under the control of means for measuring the diameter of the bale being formed.
The object of such arrangement is to provide control of at least one twine guide arm in such a manner that a bale is tied automatically when, in the course of its formation in the baler, it has reached a predetermined diameter.